The invention discloses a multipurpose water pump driven by motorcycle power, comprising a pump body shell, a pump cover, a vane wheel, a connecting shaft, a bearing, a bearing shell and a bearing end cover, wherein, the bearing shell is fixedly connected with the bearing end cover, and the end of the connecting shaft is provided with a crankshaft optimal-length transmission device; and the crankshaft optimal-length transmission device comprises a connecting rod, a transmission sleeve and an elastic device. The multipurpose water pump adopts the crankshaft optimal-length transmission device, and can be automatically adjusted according to the length of the crankshaft of the motorcycle, thereby meeting the requirement on fixed connection; the multipurpose water pump has the advantages of compact structure, low difficulty on installation, high utility ratio of power equipment and favorable flexibility, and can be especially applied to the areas with higher popularizing rate of motorcycles in China; and the invention also discloses a transmission connection method for the water pump driven by the motive power of the motorcycle.